In English you have basically three indefinite articles which are: "A" and "AN" and "SOME". We know they differ each other depending on whether the next word begins with either a consonant or a vowel respectively and in the case of "SOME" if the word is plural. However in Spanish is a little different because we have FOUR indefinite articles and they take into account GENDER and NUMBER. Pay attention to the following examples so that you get the idea:
Masculine Singular "un" : a book - an airplane / un libro - un avión
Feminine Singular "una" : a lamp - an actress / una lampara - una actriz
Masculine Plural "unos" : some books - some airplanes / unos libros - unos avionesFeminine Plural "unas" : some lamps - some actresses / unas lámparas - unas actrices
GRAMMATICAL TIP: The pluralization in spanish is basically similar to english (for the case of the regular plurals), you just need to add an "S" (e.g. books - libros) or "ES" when the noun ends with es, sh, x, ch, s (e.g. buses - buses).
Unlike english language, the spanish one doesn't have irregular plurals (e.g. child - children) therefore you don't need to worry about it; the only plural ways are "s or es".
Regarding the indefinite articles the only thing you have to do is pluralize them and that's all! (unos - masculine // unas - feminine)
That's all you need to know, just practice and enjoy it!
PD. I'm sorry if there is any mistake in english!
F.
